The non-straight cable runs also made me wonder.

The value of adding positive Ackerman, IMO, is simple to ensure you don't inadvertantly end up with negative.... which would be a bad thing.

If you're careful with the whole setup there is no reason I can see why you'd end up with negative. If your a bit sloppy (just a bit) I can see how the non-pulling wire could tighten up and cause problems.